A New, Sustainable Fight against Cooling Water Corrosion

Transcription

1 A New, Sustainable Fight against Cooling Water Corrosion Electrochemical cells with Waterline CI in Rivertop corrosion testing lab Technical Bulletin, 2.2

2 Waterline C Corrosion Inhibitor I Performance and Versatility without Compromise Rivertop Renewables introduces a new corrosion inhibitor for protection of carbon steel in industrial and institutional cooling water systems. Waterline CI provides unparalleled protection across a wide array of cooling water conditions. Waterline CI forms a persistent, passivating film on steel surfaces, does not pose a fouling concern with calcium, and eliminates the need for phosphate stabilizing copolymers. Furthermore, Waterline CI is 100% free of phosphorus, zinc and molybdenum. Phosphorus-based treatment programs are problematic, costly and face increasing regulatory pressure. Waterline CI is a cost-effective replacement for phosphorous-dependent inhibitors. Waterline C I Delivers: Superior protection of carbon steel surfaces Outstanding performance in both low and high hardness water and across a wider ph spectrum than phosphorous-based chemistries Phosphorous-free technology that does not pose fouling risk with other cooling water components Excellent compatability with other commonly used corrosion inhibitive chemistries Sodium glucarate chemistry that has been reviewed by EPA s Safer Choice Program and qualifies for use in Safer Choice-labeled products. Simplifying Corrosion Protection When chromates were banned from industrial cooling towers, the industry turned to phosphorous-based chemistries. Unfortunately, these chemistries lead to a multitude of complications: Suboptimal performance under stressed water conditions Fouling from precipitation The need for stabilizers Accelerated corrosion of zinc alloys The addition of nutrients that promote bacterial growth Phosphorous-based chemistries are facing increased pressure from regional and federal regulators to limit contamination and eutrophication of surface water. These regulations are making water more difficult and costly to treat and discharge to municipal wastewater treatment facilities and the environment. Waterline CI provides an attractive alternative to dependence on phosphorous-based chemistries. New in this Version of the Bulletin Superior Performance vs. Phosphonates in HVAC Water Better Performance in High Hardness Water Stability with Oxidizing Biocides Biostability: Does Not Contribute to Additional Microbiological Growth Waterline CI for Cooling Water - Technical Bulletin, 2.2 2

3 Performance Comparisons to Other "All Organic" Programs Waterline CI was evaluated to see how it compares to the all organic programs commonly used to treat cooling water. These included formulations containing 1-Hydroxy Ethylidene-1, 1-Diphosphonic Acid (HEDP) and 2-Hydroxyphosphonoacetic Acid (HPA). Waterline CI was applied to a phosphorous-free formulation for performance comparisons within a simulated cooling water environment. The three formulations and their operating inhibitor dosages are shown in Tables 1A, 1B and 1C. Note: the Waterline CI formulation does not require a stabilizing copolymer as the inhibitor remains stable in the presence of calcium. Tables 1A, 1B and 1C: "All Organic" Formulations The simulated cooling water chemistry and operating conditions were chosen to represent those that may be seen in HVAC systems where all organic programs are commonly used. The water was allowed to cycle-up during testing to 5.0 cycles of concentration. In addition, each system was equipped with an Oxidation-Reduction Potential (ORP) controller for maintaining a range of mg/l free chlorine within the system using a sodium hypochlorite feed. The hypochlorite was added to determine each inhibitor program s compatibility with this oxidizing biocide. The exact water chemistry and chosen parameters can be found in Table 2 (Note: Table 2 also includes reference to the same water chemistry at 8.0 cycles of concentration and treated with bromine, as will be discussed in a later section of this bulletin). Table 2: Simulated HVAC Cooling Water Chemistry and Operating Parameters Waterline CI for Cooling Water - Technical Bulletin, 2.2 3

4 In-house testing has shown that Waterline CI can provide superior performance when initially dosed into the system at an increased concentration to allow for the formation of a protective film. Higher passivating dosages of the inhibitor provide a more protective barrier to corrosion. This initial passivating dose can range from 50 to 100mg/L active inhibitor. Lower subsequent dosages are typically sufficient to maintain protection of steel surfaces. The lower maintenance dosage of 30mg/L active inhibitor can then be fed into the cooling water as part of a product formulated with additional treatment additives. The passivating dose may be administered by supplementing a fully formulated product containing Waterline CI with a direct dose of the inhibitor. Alternatively, one may increase the initial dose of fully formulated product by two-thirds to achieve 50mg/L passivating dose of Waterline CI. For these evaluations, an initial direct dose of 20mg/L active Waterline CI was first added to a simulated cooling tower water that was already treated with the Waterline CI formulation shown in Table 1C, bringing the initial passivating dosage of Waterline CI to 50mg/L active product. The cell treated with Waterline CI was then compared to the cells treated with the HEDP and HPA formulations shown in Tables 1A and 1B. Over the course of a three-day period and cycling of water chemistry up to five cycles of concentration, the Waterline CI formulation outperformed both of the phosphonate treatment programs. These test results can be found in Figure 1. Figure 1: Corrosion Rate (mpy) Waterline CI for Cooling Water - Technical Bulletin, 2.2 4

5 A More Persistent Film than Phosphate in Refinery Water Waterline CI rapidly forms a tenacious film when tested in a more aggressive water chemistry, such as cooling water conditions typically found in refineries. Waterline CI and ortho-po4 were slug-dosed into electrochemical cells and corrosion rates were monitored under the following conditions: Table 3: Simulated Refinery Cooling Water Chemistry and Operating Parameters Figure 2: The test results show that ortho-po4 begins to fail immediately, while Waterline CI maintains corrosion protection for at least 30 hours. Rivertop will continue to study Waterline CI performance in refinery-type water to determine what dose rate is recommended to achieve sufficient corrosion protection. Waterline CI for Cooling Water - Technical Bulletin, 2.2 5

6 Better Performance in High Hardness Water Waterline CI outperforms the phosphonate-based formulations in high hardness water, where phosphonates such as HEDP and HPA struggle. It is well known that HEDP and HPA both have poor calcium tolerance and tend to precipitate out with calcium in high hardness water. In addition, the majority of the corrosion inhibition properties for both products is frequently derived from ortho- PO4 that is generated from each product due to its degradation in the presence of oxidizing biocides. This generated PO4 also requires stabilization in high hardness water. Waterline CI eliminates these precipitation risks and provides simplicity in corrosion protection. Waterline CI was compared to an HEDP-based program in high-cycle simulated cooling water. The exact water chemistry and parameters can be found in Table 4 below. Table 4: Simulated High Hardness Cooling Water Test Conditions and Operating Parameters Each test solution was dosed to achieve the concentrations show below in Figure 3. In order to simulate the ortho-po4 generally derived from HEDP when used with oxidizing biocides, 3.0mg/L PO4 was added into the phosphonate formulation. Test results indicate a low and stable corrosion rate using the Waterline CI formulation where the HEDPbased formulation was much more erratic in its behavior and maintained slightly higher corrosion rates throughout the last half of testing. These results can be seen in Figure 3 below. Figure 3: Waterline CI for Cooling Water - Technical Bulletin, 2.2 6

7 In addition, the HEDP-treated system experienced a loss of reverted ortho-phosphate. This is attributable to calcium phosphate precipitation that the AA:AMPS copolymer could not control at such high calcium phosphate saturations. These results can be seen in Figure 4, which shows a gradual decrease of soluble ortho-po4, along with a coinciding increase in suspended ortho-po4. Figure 4: Precipitated Calcium Phosphate in an HEDP Treated System Excellent Calcium Tolerance Compared to other Phosphonates and Polyacrylate It is well known that phosphonates and polyacrylates exhibit poor calcium tolerance in systems where the cooling water is cycled up to high concentrations of calcium due to water conservation and waste water discharge regulations. Waterline CI shows excellent calcium tolerance at calcium concentrations well above those typically encountered in cooling water conditions. It has been found to be remarkably stable at product concentrations above 1000mg/L active product and calcium concentrations of over 5000mg/L as Ca 2+. The calcium tolerance of Waterline CI was compared to that of other common chemistries used in cooling water applications. For these evaluations, the calcium concentration was held at a constant level of 200mg/L as Ca 2+, while the product dosage was increased. The following graph highlights the superior calcium tolerance demonstrated by Waterline CI as it compares to these other standard chemistries: Polyacrylic acid (PAA) 2-Phosphonobutane 1,2,4-tricarboxylic acid (PBTC) 2-Hydroxyphosphonoacetic Acid (HPA) 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid (HEDP) Waterline CI for Cooling Water - Technical Bulletin, 2.2 7

8 Figure 5: Less Aggressive to Galvanized Metal While ortho-po4 is commonly used as a treatment for galvanized systems, it can also be aggressive to the zinc coatings. Testing demonstrates that Waterline CI is not aggressive to zinc surfaces and does not increase zinc corrosion rates. This is demonstrated by testing recommended water conditions for passivating a galvanized system (Table 5), as shown in Figure 6. Table 5: Simulated Galvanized System Cooling Water Test Conditions and Operating Parameters Waterline CI for Cooling Water - Technical Bulletin, 2.2 8

9 Figure 6: The resulting corrosion rates for Waterline CI indicate no measurable attack of the zinc coating when compared to an untreated system. In contrast, ortho-po4 maintained higher corrosion rates throughout the test. The following photographs further demonstrate that Waterline CI does not promote white deposits that could lead to pitting on zinc surfaces. A simulated galvanized system with the water conditions noted above and treated with Waterline CI resulted in a zinc electrode free of white deposits. The same system under the same conditions was fouled with white deposits when left untreated or treated with phosphate. No inhibitor Ortho-PO4 Waterline CI Excellent Stability to Hypochlorite Waterline CI was evaluated to see how it would perform when subjected to higher concentrations of free chlorine. For these evaluations, the free chlorine was intended to be fed within a range of mg/L free chlorine. The Waterline CI formulation, along with an additional 20.0mg/L active passivating dosage, was compared to the HPA formulation (shown in Tables 1B and 1C above). Figure 7 indicates the concentrations of free chlorine measured during each evaluation. Note that there was a significant degree of inadvertent hypochlorite overfeed during the testing of the Waterline CI formulation; free chlorine concentrations reached concentrations greater than 1.0mg/L for a good portion of the first three days of testing. Waterline CI for Cooling Water - Technical Bulletin, 2.2 9

10 Figure 7: Figure 8 below indicates corrosion rates measured during the course of each test. Note that despite the initial overfeed of hypochlorite, the Waterline CI formulation outperformed the HPA formulation. The graph also indicates the measured concentrations of soluble orthophosphate found in the test water from the system treated with the HPA formulation. It is well known that HPA degrades in the presence of oxidizing biocides and increasing orthophosphate concentrations are indicative of this degradation. Though orthophosphate concentrations reached as high as 7.0mg/L and had 10.0mg/L AA:AMPS copolymer present for stabilization, it was still unable to match the corrosion protection of the phosphorous-free Waterline CI formulation. Figure 8: Waterline CI for Cooling Water - Technical Bulletin,

11 Excellent Stability to Stabilized Bromine Due to its greater effectiveness in alkaline cooling water systems, bromine is often chosen as a biocide for higher ph cooling water conditions. A common method of treating with bromine is through the use of a stabilized product. The Waterline CI formulation, along with an additional 20.0mg/L active passivating dosage, was tested to evaluate its performance compared to a phosphonate treatment, when both were subjected to a stabilized bromine product. The water chemistry chosen was that seen in Table 2 as eight cycle water. The stabilized bromine product was fed to achieve 20ppm total bromine with each slug dosage, which was then allowed to dissipate over time until the measureable free bromine values dropped below 1.0mg/L free bromine. This method resulted in a fresh stabilized bromine slug-feed into the system of once every couple of days. There was no noticeable spike in corrosion rates for either treatment with each concurrent slug dosage of biocide. Both treatments appeared unaffected by the high dosage of total bromine. However, the Waterline CI-based treatment provided lower corrosion rates initially during testing, before reaching a steady corrosion rate similar to that of the phosphonate-based treatment. These results can be seen in Figure 9. Figure 9: Waterline CI for Cooling Water - Technical Bulletin,

12 Biostability: Waterline C I Does Not Contribute to Additional Microbiological Growth Rivertop acquired samples of conventionally treated water from two distinct cooling towers as sources of relevant microbiological species. For each cooling tower sample two different aliquots of the cooling tower water were incubated for bacterial growth under laboratory conditions of controlled temperature and aeration. Waterline CI was added to the first aliquots at a concentration of 100mg/L. Nothing was added to the second aliquots ( blank ). Dip-slides designed to monitor bacteria and fungi growth were used to calculate the colony density of the four aliquots. The dip-slides were immersed in each of the aliquots upon initial mixing and every 24 hours for a full week and then held at ~27 C for up to 4 days with daily examination of growth. The bacterial colonies were quantified following 36 hours of growth and the fungi growth was quantified after 4 days. Both samples of cooling tower water showed similar results. There was no presence of fungal growth in any of the aliquots over the testing period. There was a slight retardation of bacterial growth in the first day in the presence of Waterline CI, most likely due to the microbiome being conditioned to metabolize the components present in the water before Waterline CI addition. This slight difference became insignificant after the first 2 days of growth. The addition of Waterline CI to the samples of cooling tower water did not cause significant changes to the growth rate or quantity of bacteria in the sample over the testing period. Figure 10: ANY TECHNICAL ADVICE OR INFORMATION PROVIDED BY RIVERTOP TO THE CUSTOMER, WHETHER VERBALLY OR IN WRITING, IS PROVIDED AS IS AND WITHOUT ANY EXPRESS, IMPLIED OR STATUTORY REPRESENTATION OR WARRANTY OF ANY KIND. THE CUSTOMER SHALL BE RESPONSIBLE FOR TESTING AND VERIFYING THAT RIVERTOP S PRODUCTS AND/OR SERVICES ARE SUITABLE FOR THE CUSTOMER S INTENDED APPLICATIONS, PROCESSES AND USES. THE CUSTOMER S APPLICATION, USE AND PROCESSING OF RIVERTOP S PRODUCTS AND/OR SERVICES ARE BEYOND RIVERTOP S KNOWLEDGE OR CONTROL AND, THEREFORE, ALL USES OF SUCH PRODUCTS [AND/OR SERVICES] ARE ENTIRELY THE RESPONSIBILITY OF THE CUSTOMER. IN NO EVENT SHALL RIVERTOP BE LIABLE TO THE CUSTOMER FOR ANY CONSEQUENTIAL, INCIDENTAL, OR INDIRECT DAMAGES, INCLUDING ANY DAMAGES FOR BUSINESS INTERRUPTION, LOSS OF USE, DATA, REVENUE OR PROFIT, WHETHER ARISING OUT OF BREACH OF CONTRACT, TORT (INCLUDING NEGLIGENCE) OR OTHERWISE, REGARDLESS OF WHETHER SUCH DAMAGES WERE FORESEEABLE AND WHETHER OR NOT RIVERTOP WAS ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. FURTHER, IN NO EVENT SHALL RIVERTOP S AGGREGATE LIABILITY TO THE CUSTOMER FOR ANY CLAIM OR LOSS ARISING OUT OF OR RELATED TO ITS PRODUCTS [AND/OR SERVICES] EXCEED THE TOTAL AMOUNT PAID BY THE CUSTOMER TO RIVERTOP FOR THE PRODUCTS [AND/OR SERVICES] GIVING RISE TO SUCH CLAIM OR LOSS. COPYRIGHT RIVERTOP RENEWABLES, INC. ALL RIGHTS RESERVED. RIVERTOP, THE RIVERTOP RENEWABLES LOGO, AND WATERLINE ARE TRADEMARKS OF RIVERTOP RENEWABLES, INC. Waterline CI for Cooling Water - Technical Bulletin,